Thetford toilet sewer smell

There are two gaskets that can cause a gas leakage in a toilet- one is the floor flange to base gasket, and the other is the flush valve to bowl gasket. Some toilets have an additional gasket between the riser and the bowl, but not all. Replace all the gaskets, I've only had mine last 4-5 years before they stop being gas tight.

The tank is always going to stink, it's designed to do that- it's a big tank full of poop. The trick is to keep the stink confined to the tank and/or vent, out of the bathroom.


I like to wait until the winter to maintain my toilet, then the smell isn't so bad when I have to remove it.

I had same problem with Aqua magic V toilet. I did the flushing of tank two years ago, did not help. Changed floor seal last year, thought that fixed it. Then got the smell again this year. I read about that there is a seal on the back of the toilet near top that tends to leak after a few years. It can not be replaced. I went to Amazon bought a new Aqua Magi V for around $120 dollars and a Cyclone vent cover for around $20. Less than two hours to install both. That was in the spring of this year and no smells... fingers crossed.

What model toilet do you have? My Thetford AquaMagic IV leaked sewer odor. It's a crummy toilet design that is prone to leaking stinky odor.

Where does you vent run? Is it possible the vent pipe isn't properly sealed to the tank?

Behind the toilet is a strange source.

Check the vent going through the roof

Thanks for all of the replies. Here is what I have done. I have checked all of the vents including the one under the vanity sink.
I have thoroughly cleaned the tank with a wand.
I live in my trailer so I am connected to a septic tank. I keep the grey water tank valves open but close the black water tank valve. I understand that it is good to keep water in that tank so it will not dry out.
I put a tank order product in the toilet everytime after I empty the tank.
Everything is fine for about two weeks and then an order starts coming from behind the toilet. I have pinpointed it there.
I am thinking about changing out the toilet flange seal.

Maybe pull the toilet and inspect, clean, and install a new gasket. Very easy to re & re these toilets. (Do not re-install the gasket if you pull the toilet.)

If your not going to use your rig for a week or so consider buying a septic tank cleaner available at hardware store. Add the cleaner and fill the black water tank to the top - give it at least a week and the cleaner should dissolve all the crud in the tank ... then dump. It's not expensive/easy to do -- just takes some time.

DutchmenSport wrote:
Push the pedal on your toilet and get a toilet brush down inside the neck of the toilet.

More easily accomplished using a tank wand which washes down not only the interior walls of the black water tank but also the toilet throat.

If odours persist and you're convinced it's not a leaking seal you need tank maintenance - try Walex Commando ... I do a couple times each season and have no issues with tank odour. :B

Cleaned the tank multiple times and it still smells?
Fill it all the way up with water and odor control packet, let it sit and see if it still smells.

Maybe its a small propane leak. I had that once and thought it was sewage.

Im fighting an actual black tank leak myself....yuck.